(1) Field of the Invention
The present invention relates to an image forming apparatus with multiple functions integrated within, such as printer, copier, scanner and other functions.
(2) Description of the Prior Art
Recently, there is an image forming apparatus which integratedly has printer, scanner and other functions and can be used in connection with computers, the telephone line and the like. These individual components are combined so as to constitute an integrated image forming apparatus having multi-functions, as printer, copier, scanner and other functions.
In general, in an image forming apparatus having multiple functions as stated above, function selection keys are laid out on the control portion and are used to select a function, either copier or printer, whereby one mode corresponding to the selected function is set up.
The structure of the body of such an image forming apparatus having multi-functions is liable to be bulky.
On the other hand, there have been demands for miniaturization of the apparatuses of this type. Therefore, each component needs to be down-sized, and the optical system including first and second mirrors, a focusing lens and an image reading element (CCD element) also needs be made compact.
As a prior art example of this technology, an image reading apparatus having an optical system including first and second mirrors, a focusing lens and an image reading element (CCD element) is disclosed in patent publication of Japanese Patent No. 2,684,363.
In this apparatus, an original set on an original table in the upper part of the image reading apparatus is conveyed facedown by means of original conveying rollers which are provided on both upstream and downstream sides of the original table, and is illuminated at the image reading position with light by an illuminating lamp. The image of light from the illuminated original is reflected by the first mirror to reach the second mirror. Then the light reflected by the second mirror is focused on the CCD element via the focusing lens.
In this apparatus, the second mirror, the lens and the CCD element are laid out on the same plane which is approximately in parallel with the surface of the original so as to make the structure compact.
The above case of the prior art, however, has suffered from a problem in that paper dust, arising from the original documents when they are conveyed in contact with the original conveying rollers, enters the machine interior through small structural gaps around the original conveying rollers, to thereby stain the surfaces of the first and second mirrors and focusing lens in the optical system, causing failure to exactly read the original image. Further, since the optical system was fixed to the machine main body, it was difficult to clean the optical system.
As another prior art example, there is an image forming apparatus which has been manufactured by the company of the present applicant. This apparatus has an optical system including first, second and third mirrors, a focusing lens, an image reading element (CCD), in which the reflected light from the original is reflected multiple times between the second and third mirrors so as to obtain a required optical path length.
In the case of this prior art, since the second and third mirrors need to be large, this makes the apparatus body bulky.
Further, since multiple reflections markedly attenuate the strength of the reflected light from the original, the light intensity of the light source needs to be high to compensate for this attenuation. However, the increase in light intensity induces another risk that the original image reading position might be heated excessively, possibly burning the original document that is conveyed.